It is well known to utilize fluid filter assemblies to filter fuel for a combustible engine of a motor vehicle. Such fluid filter assemblies comprise a variety of different orientations of the fluid filter assembly. For example, it is known to utilize sideways, downwardly, and upwardly mounted canisters having a paper filter media enclosed in the canister to form the fluid filter assembly. With respect to upwardly mounted fluid filter assemblies, prior art filtration devices have been known to provide fuel to the fluid filter assembly by use of a pump. The fuel is directed downward into a lower chamber of the fluid filter assembly wherein the fuel flow proceeds upward into an upper filter chamber of the fluid filter assembly. The fuel may then be contained and sealed by a transparent cover or enclosure of the fluid filter assembly for viewing the fuel level within the upper filter chamber. A filter mount separates the lower chamber from the upper chamber of the fluid filter assembly.
Within the filter chamber of the fluid filter assembly, the fluid filter assembly may provide a filter canister comprised of a filter media that is contained by filter end caps at the top and bottom of the filter media. The filter media may, optionally, encircle a central filter tube that provides additional support for the filter media. The end caps are sealed to the edges of the filter media to preclude any possible leak paths at the ends of the filter canister. The filter media typically comprises a meltblown plastic material or a porous paper material that may be pleated or concentrically wound so as to direct the fluid through the filter media. The filter media removes undesirable contaminants from the fuel by retaining the contaminants within and on the filter media.
As fluid enters the filter chamber, the fuel level rises and passes through from the outside to the inside of the filter media. The fuel then flows downward into a central passage located along the central axis of the canister. The central passageway is in communication with a fuel outlet wherein the fuel passes outwardly from the fluid filter assembly.
During the filtering process, the fuel is either drawn into the filter chamber by a vacuum created by a pump downstream from the fluid filter assembly, or the fuel may be pushed into the filter chamber by pressure created by a pump upstream from the fluid filter assembly. As the fuel flows through the filter media, dirt and other contaminants larger than the porous openings in the filter media are trapped and retained by the filter media. These contaminants plug or clog the porous holes in the filter media and restrict or close the paths used by the flowing fuel. The fuel is then forced to seek other open and less restrictive flow openings which are available above the level of the fuel by having the fuel level climb the height of the filter media and access the clean areas of the filter media. This process of clogging and climbing continues until the filter media is completely immersed in the flowing fuel.
Even though the filter media may be completely immersed in the flowing fluid, the incoming fuel continues to pass through the filter media. It is not until the filter media becomes greatly clogged that the filter canister needs to be replaced. This is a problem since the user generally views the height of the fuel in the filter chamber to determine if the filter media is clogged. If the filter media is completely immersed in fuel, the user generally believes that the filter canister needs to be replaced. Therefore, this type of system may lead to premature replacement of the filter canister.
It is known that the system described above may be improved upon by providing a divider and a pressure relief valve on the filter canister. The divider is connected to a top end cap of the filter canister and wraps around the filter media. It functions to divide the portion of the housing adjacent to the filter media into an inner region that is defined between the filter media and the divider, and an outer region that is defined between the divider and the housing. The divider allows the fluid in the inner region to rise fully before the fluid in the outer region begins to rise. The fluid in the outer region rises when fluid and/or air/vapor passes through the pressure relief valve when the pressure across the filter media exceeds a predetermined pressure. The pressure relief valve is mounted in an end cap of the filter canister. While this system provides a more accurate indication of the remaining life of the filter media, the complexity and the cost of the filter canister is increased over previous designs by its incorporation of a divider and a pressure relief valve. Since the filter canister is routinely replaced when the filter media becomes clogged, the increased cost of the filter canister is an undesirable factor in maintaining the fluid filter assembly.
Furthermore, in the systems described above, it is common to mount the filter upon an outlet pipe that is formed on a base portion of the fluid filter assembly. The filter is typically biased into engagement with the base portion and the outlet pipe by using a spring that engages the cover of the fluid filter assembly as well as a top end of the filter canister. In such systems, the filter cartridge can be installed such that it is not perfectly aligned along the filter cartridge axis defined by the outlet pipe of the base portion of the fluid filter assembly, resulting in uneven exposure of the filter media to the fluid within the fluid filter assembly and potentially reducing the accuracy of the visual indication of remaining life provided by the fluid level within the fluid filter assembly.
It would be desirable to provide a fluid filter assembly that provides an accurate indication as to the remaining usefulness of the filter media while reducing the complexity and cost of replacing the fuel filter canister. It would also be desirable to provide a fluid filter assembly that provides for accurate axial alignment within the fluid filter assembly.